Fuel injection devices for internal combustion engines



C. M. BOVARD May 21, 1957 FUEL INJECTION DEVICES FOR INTERNAL COMBUSTION ENGINES Filed April 6, 1955 2 Sheets-Sheet 1 A mu 20mm? EOdu INVENTOR Cfiaf/ea M al 4rd y 1957 c. M. BOVARD 2,793,077

FUEL INJECTION DEVICES FOR INTERNAL; COMBUSTION ENGINES Filed April 6', 1955 2 Sheets-Sheet 2 l I l I /2 50 V 1/ l4 5 Q 70 I Ii I I. n i N c 3 60-, k 024w W a 1 l 76 5/ I 26' /8/ i ll 20 //0' V v INVENTOR. Z Chans M Howard United States Patent FUEL INJECTION DEVICES FOR INTERNAL COMBUSTION ENGINES Charles M. Bovard, Mount Vernon, Ohio, assignor to The Cooper-Bessemer Corporation, Mount Vernon, Ohio, a corporation of Ohio Application April 6, 1955, Serial No. 499,559 1 Claim. (Cl. 299107.2)

This invention relates to fuel injection devices for internal combustion engines and is particularly directed to an improved means to accumulate a measured fuel charge and to inject the charge into an engine cylinder under a pressure greatly in excess of the pressure at which the charge was accumulated.

It has heretofore been proposed to provide accumulator fuel injectors in which fuel is accumulated under very high pressure on both sides of a movable wall and subsequently injected under the pressure at which it was accumulated by opening a discharge valve which has the effect of suddenly releasing the pressure on one side of the movable wall which then acts as a piston to force the fuel charge into and through a discharge line to an injection nozzle. Such devices have the disadvantage that the high pressure on the fuel charge must exist for an unnecessarily long period so that the liability of leakage is greatly increased, and also are disadvantageous in view of the necessity of opening a discharge valve against a very high pressure.

The primary object of the present invention is to provide an injector in which fuel is accumulated at relatively low pressure by means of a variable pressure pump, stored in the accumulator chamber and subsequently in jected at high pressure by an actuating fluid from 21 separate, high pressure pump.

The invention is particularly applicable to the injection of fuel in free piston machines for the reason that the accumulation of a fuel charge can be made during either the outward stroke of the pistons or the early portion of the inward stroke and injection of the fuel may be caused at the extreme end of the inward stroke. Because injection takes place under a fluid pressure that can be developed entirely apart from any device that is moved in timed relation to the engine piston such as a constantly driven pump, the fact that piston motion has virtually stopped at the time fuel is injected into the engine cylinder has no effect on the injection characteristics.

Another object of the present invention is to provide an accumulator type fuel injector in which the quantity of fuel metered into the accumulator cylinder is variable in accordance with a simple input pressure and is independent, in quantity, of any mechanical movement that may be derived from the engine. In free piston engines wherein the length of the piston stroke varies with the load on the machine it is highly desirable to divorce the function of fuel metering from devices that depend for their functioning on the extent of the stroke of the pistons of the machine.

Other objects and advantages of the invention will be apparent from the following specification which describes a preferred embodiment thereof, reference being had to the accompanying drawings, in Which-- Fig. 1 is a diagrammatic View, with parts broken away, of a free piston engine equipped with a fuel injection system incorporating the present invention;

Fig. 2 is a somewhat diagrammatic, vertical sectional 2,793,0 7'7 Patented May 21, 1957 view of a control valve used with the injector of the present invention; and

Fig. 3 is a somewhat diagrammatic vertical sectional View of a fuel injector incorporating the present invention.

Referring to Fig. 3, a fuel injector is shown somewhat diagrammatically as comprising a body 10 having an upper cap extension 12 fastened thereto by bolts 14 and a lower nozzle carrying extension 16. The body 10 is formed with a central accumulator cylinder 18 which may be of any suitable construction but preferably comprises a lapped liner 20 seated against a hardened and ground end member 22. The bore of the liner 20 which constitutes the actual accumulator chamber is designated 24 and receives an accumulator and injector piston 26.

The piston 26 is urged into the accumulator cylinder by a spring 28 which bears at its outer end against a stop member 30 the shank of which extends within the coils of the spring in the path of the upper end of the piston. The spring and stop member are disposed within a bore 31 in the cap extension 12, the bore being sealed off so that it can contain high pressure actuating fluid. The parts are shown in the drawing in the position that would be occupied by the accumulator piston 26 at the end of the accumulating portion of its cycle of operation with the maximum quantity of fuel metered into the accumulator chamber 24. At part load the ultimate upper position of the piston 26 is such that no contact will occur between its end and the stop member 30, be cause, as will be hereinafter described, the quantity of fuel accumulated is made to depend on the pressure at which the accumulation is made, this pressure being balanced by spring 28. For different engines the characteristics of the spring 28 will be varied by making it longer or shorter, stiffer or less stiff so that the range of accumulating pressures is changed. For this reason the axial extent of bore 31 is indefinite as indicated in dotted lines.

The lower end of the accumulator chamber 24 com municates by a passage 32 with a bore 33 in which is disposed a spring 34 pressing against an inlet check valve 36. The valve 36 controls an inlet passage 38 which extends outwardly of the injector and is coupled to the discharge of a suitable variable pressure fuel pump P1 (Fig. 1). Pump P is a low pressure device, the output pressure of which is variable between 200 p. s. i. to 400 p. s. i.

The bore 33 also communicates with a. discharge passage 40. The passage 40 runs out of the body 10 to enter an injection nozzle generally designated 42. Nozzle 42 may be of any suitable construction, and many satisfactory devices are known in the art. The device shown in the drawings includes a needle valve 44 which cooperates with a seat 46 to close off a passage 48 leading to the end of the nozzle and thus to the: interior of an engine cylinder in which the entire unit is mounted. The needle valve is carried at the end. of a plunger 50 and the plunger and valve are urged to closed position by a spring 52 disposed in a chamber 54 which is maintained at atmospheric pressure by connection to a drain line through a small lateral passage 56. The entire nozzle is held in place with respect to the injector body by a sleeve 60 threaded to the body extension 16 and having a lower internal flange 62 that bears against a shoulder of the conventional nozzle tip 64.

Above the piston 26 the bore of the accumulator cylinder communicates with an operating fluid inlet passage 70. This passage extends outwardly from the injector body and communicates with the discharge of a high pressure pump P2. The piston 26 is preferably provided with a relief groove 72 on its periphery which communicates with a central relief passage 74 opening at the top of the piston into the chamber or bore 31.

The relief groove is spaced from the lower or inner end of the piston 26 a distance such that, when the piston is at the end of its movement and is standing against the end member. 22, the groove registers with a series of peripherally spaced communicating relief ports 76in the wall of the accumulator cylinder liner 20. The relief ports, in turn connect with a drain passage 78 and outlet 80.

Figure 1 of the drawings shows diagrammatically a free piston engine and its fuel system including the present invention. The engine includes the usual opposed piston sets 100 and 101 including the usual large compressor pistons 102 and 103. The compressor pistons are each provided with a rack 104 extending outwardly along the central part of the engine and meshing with a synchronizing pinion 105. The fuel injector body is indicated by its numeral and is disposed between the piston sets 100 and 101 to inject fuel into the combustion chamber formed thereby.

As diagrammatically shown in Fig. 1, one of the racks 104 may be provided with cams 106 and 107 at positions corresponding to the inner and outer positions of the piston sets. Carn 106 operates a valve 108 whenever the pistons are at the outer end of the stroke, and valve 108 admits fuel from the low pressure (200 p. s. i. to 400 p. s. i.) pump P1 through a manual or automatically controlled regulator valve 111 into the fuel accumulator or inlet line or passage 38.

Cam 107 is disposed on rack 104 (although it may be mounted on either rack) at a position corresponding to the inner end of the stroke of the pistons when injection is desired. Cam 107 operates a valve 112 in a line from the high pressure pump P2 to the high pressure activating fluid line 70 so that fluid is admitted to line 70 whenever the earn 107 depresses the valve 112 and continues to exert its pressure so long as the valve is open.

The valve designated generally 112 in Fig. 1 is shown in greater detail in Fig. 2. The valve serves the purpose of admitting a pulse of high pressure oil to line 70 to drive the piston 26 downwardly and cause injection of the metered fuel charge. The valve comprises a head 113 normally closed against a seat 114 and carried at the end of a reciprocable body 115 having a plurality of guiding ribs 116 disposed in grooves in the body of the valve housing. The valve is thus guided and restricted to purely rectilinear movement. At its upper end the valve engages a plunger 117 and while engaged closes off a pressure relief passage 118 disposed centrally of the plunger and extending into a peripheral relief groove 119 which, in turn, communicates with a drain line.

When valve head 113 is forced off its seat by cam 107 acting through a suitable follower and through plunger 116, high pressure oil is admitted to line 70 to cause injection as above described. This high pressure oilwill continue to flow so long as the valve head 113 is 01f its seat 114 and after the piston 26 has reached the end of its stroke the flow will be through relief passage 74, groove 72 and drain passage 80 in the injectorbody. When the cam 107 releases the plunger 116 so that valve head 113 can re-engage its seat, the plunger 116 becomes a pressure relief valve for the chamber above the accumulator piston 26, since oil can move out of this chamber back through line 70, around the valve body 115 and between this body and the lower face of the plunger 116 to enter the relief passage 118 and relief groove 119 to drain away. In this manner the piston 26 is free to move up under the influence of the next accumulated fuel charge without danger of being locked hydraulically by oil above it. Thus the only resistance to the accumulation of fuel is imposed by the calibrated spring 28 above the piston.

In operation, fuel under relatively low pressure (200 400 p. s. i.) is admitted to the injector from pump P1 to the inlet line 38 past the inlet check valve 36 and into the accumulator chamber 24. Fuel Will continue to flow into the chamber until the spring 28 has been deformed to the point where its force exactly balances the pressure of the low pressure charging pump as determined by the setting of regulator valve 111. A predetermined quantity of fuel has thus been accumulated irrespective of the duration of the opening of the valve which controls the passage between the charging pump discharge and the injector inlet. Thus, in a free piston machine in which the cam 106 which controls the valve is on or driven by the synchronizing rack 104, the fact that the valve is opened during the outward stroke and again during the inlet stroke is immaterial since the quantity of fuel accumulated is a function of pressure and not of time.

Once the fuel charge has been accumulated in chamber 24 beneath piston 26 it remains there until actuating fluid is admitted through passage 70 above the piston 26. This fluid is taken from the high pressure pump P2 and communication is established by the cam controlled valve 112 which is opened at the inner end of the stroke of the free pistons. The pressure may be several thousand pounds per square inch, greatly in excess of the pressure at which the charge has been accumulated. The high pressure forces the piston 26 down and forces the fuel out of the accumulator chamber 24, through discharge passage to the space below the plunger lifting the same against its spring 52 and thus raising the needle valve 44 from its seat. The charge is thus injected through passage 48 into the engine cylinder.

It will be seen that injection of fuel will continue only during the stroke of piston 26 regardless of the fact that high pressure may be maintained above it for some time thereafter, and that a positive stop to the injection occurs when the piston 26 strikes the hardened end member 22. This is also a distinct advantage in free piston engines because the cam 107 which controls the opening of valve 112 in the high pressure line is at the position on the synchronizing rack corresponding to the inner end of the piston stroke and thus acts to hold the valve open not only during the last portion of the inward stroke when it is desired, but also for a corresponding period during the outward stroke before which injection should have been completed.

What I claim is:

In a fuel injector, the combination of means defining an accumulator chamber and including a piston defining one side of said chamber, said accumulator chamber having a peripheral pressure relief opening, and said piston having a pressure relief groove registering with said opening when said piston is at the limit of its movement into said accumulator chamber, spring means resisting movement of said piston in a direction tending to enlarge said accumulator chamber, means to introduce fuel into said accumulator chamber beneath said piston at a predetermined pressure against the force of said spring means until the pressure of accumulation balances the force of said spring means, an injection nozzle, and hydraulic means to force fuel out of said accumulator chamber through said injection nozzle under pressure much higher than the pressure at which it was accumulated, the pressure of said hydraulic means being relieved whensaid piston strikes the opposite wall of said accumulator chamber and is in the position of registry between its relief groove and the relief opening in said accumulator chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,274,315 Amery Feb. 24, 1942 

